Conventional Scanning Electron Microscopes (CSEMs) require most samples to be dried of all water, and then coated with metal or carbon. This treatment generally precludes the study of dynamic events, such as the effects of dissolution.
In contrast, Environmental Scanning Electron Microscopes (ESE microscopes) and similar variable pressure microscopes, allow samples with a high moisture content to be imaged. Within an ESE Microscope, the samples are imaged by introducing water vapor into the chamber, and ionizing the vapor cloud directly over the sample. By controlling both the chamber pressure and the sample temperature, the sample can be maintained in a water saturated state.